Effect of chromatin-modifying agents on ex vivo expansion of CB-EPCs. (A) Effect of chromatin-modifying agents on ex vivo expansion of CB-CD34⁺: CD34⁺ cells were isolated from 5 individual CB units and treated with different HDACIs including SAHA (1μM), VPA(1mM), and TSA (1nM) and their effect on the number of CD34⁺ and CD34⁺CD90⁺cells following 7 days of culture was determined. The fold expansion of CD34⁺and CD34⁺CD90⁺ cell numbers was determined by dividing the total numbers of viable cells expressing the phenotype by the number of primary cells expressing the same phenotype multiplied by 100. A significant difference was observed between degree of expansion of CD34⁺cells (P = .01) and CD34⁺CD90⁺ cells (P = .02) obtained with VPA-containing cultures compared with cultures containing cytokines alone (n = 5). (B) Effect of HDACIs on the absolute number of BFU-E + CFU-Mix: CD34⁺ cells from 5 individual CB collections treated with cytokines and SAHA (1μM), VPA (1mM), or TSA (1nM) for 7days. The numbers of hematopoietic colonies were enumerated after 14 days. A greater number of BFU-E + CFU-Mix were generated in the presence of cytokines plus each of the HDACI (VPA, P = .002; SAHA, P = .04; and TSA, P = .08) compared with cultures containing cytokines alone. ■, BFU-E + CFU-Mix. (C) Effect of VPA on the fate of a single CD34⁺ cells: single primary CD34⁺cells and/or CD34⁺ isolated after 7 days of culture in the presence of cytokines alone and/or cytokines + VPA were deposited into 96-well plate in triplicate and supplemented with SCF, Epo, and IL-3. The number and types of HPC (BFU-E, CFU-Mix, and CFU-GM) were determined after 14 days of incubation (*P = .005; n = 3).